title: Depth dependence of the single chamber response function of the I'mRT MatriXX array in a 6 MV photon beam.
abstract: One of the factors which influence the spatial resolution of a 2D detector array is the size of the single detector, another the transport of the secondary electrons from the walls into the measuring volume. In this study, the single ion chamber dose response function of an I'mRT MatriXX array was determined by comparison between slit beam dose profiles measured with the array and with EBT2 radiochromic film in a solid water-equivalent phantom at a shallow depth of 0.5cm and at a depth of 5cm beyond the depth dose maximum for a 6 MV photon beam. The dose response functions were obtained using two methods, the best fit method and the deconvolution method. At the shallow depth, a Lorentz function and at 5cm depth a Gaussian function, both with the same FWHM of 7.4mm within limits of uncertainty, were identified as the best suited dose response functions of the 4.5mm diameter single array chamber. These dose response functions were then tested on various dose profiles whose true shape had been determined with EBT2 film and with the IC03 ionization chamber. By convolving these with the Lorentz kernel (at shallow depth) and the Gaussian kernel (at 5cm depth) the signal profiles measured with the I'mRT MatriXX array were closely approximated. Thus, the convolution of TPS-calculated dose profiles with these dose response functions can minimize the differences between calculation and measurement which occur due to the limited spatial resolution of the I'mRT MatriXX detector.
authors.affiliation: Department of Physics, College of Science, Qassim University, Saudi Arabia; School of Physics, Universiti Sains Malaysia, Penang, Malaysia. Electronic address: salashra@gmail.com.
authors.forename: Saleh
authors.initials: S
authors.lastname: Alashrah
authors.forename: Sivamany
authors.initials: S
authors.lastname: Kandaiya
authors.forename: Liang Soo
authors.initials: LS
authors.lastname: Lum
authors.forename: Soon Keong
authors.initials: SK
authors.lastname: Cheng
mesh_terms: D004867:Equipment Design; D019544:Equipment Failure Analysis; D017785:Photons; D011829:Radiation Dosage; D011874:Radiometry / Q000295:instrumentation*; D020266:Radiotherapy, Conformal / Q000295:instrumentation*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014159:Transducers
keywords: Gaussian kernel; Gauß-Funktion; I’mRT MatriXX array; I’mRT-MatriXX-Array; Lorentz kernel; Lorentz-Funktion